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Archive for the ‘cytokines’ Category

covid19: autopsy analyses, biomarkers, von Willebrand factor

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von Willibrand factor, a multimeric blood protein which plays a central role in blood clotting

Canto: So we’re working hard to get through what has been reported on medcram update 95, even though it’s taking us further behind the times in terms of what’s happening in the fight against this virus – there’s been some controversy on convalescent plasma recently for example – because it’s important to get the most out of every report before going onto the next one.

Jacinta: Yes, which means we need to work harder and faster. So in this study of a number of fatal cases of covid19 they found ‘no endothelial abnormalities on microscopic review, in alignment with previous studies’, which suggests that evidence of endothelial damage just doesn’t seem to be there, but they couldn’t rule out pro-coagulant endothelial dysfunction in the absence of ‘histopathological evidence of cell activation or erosion’, and they referred to another autopsy study with specialised equipment which ‘demonstrated ultrastructural endothelial damage’. So it seems they’re struggling with causes.

Canto: What they call the precise aetiology of the disease. 

Jacinta: Yes that’s what we’re after. So they do mention elevated troponin in covid19, which appears to be found regularly. Troponins are ‘a group of proteins found in skeletal and cardiac muscle fibres that regulate muscular contraction’. As the update tells us, troponin tests measure cardiac-specific troponin in the blood as a sign of heart injury. This Australian site tells us more:

For patients who are hospitalised with COVID-19, mild elevation of troponin is common (19.7%) and frequently correlates with disease severity, acting as a marker for cardiac injury. The cause of troponin elevation in serious infection is multifactorial.

In the study under discussion, they consider that the elevated troponin has to do with ‘thrombosis of the microvasculature and cardiac veins’. This cardiac vein finding is apparently important – they found, they believe for the first time, that thrombosis of a cardiac vein can cause myocardial infarction. They also write about renal findings in their subjects, to ‘shed light on the pathogenesis of acute kidney injury in covid19’. They found virions in proximal tubular cells. A virion is essentially a full, active molecule of a virus (there’s still some disagreement about these definitions, it seems). The proximal tubules are components of nephrons, the most important functional units of kidneys. They found acute tubular necrosis and other damage, and noted that this was common to other covid19 autopsy findings, perhaps unsurprisingly as these tubular cells present ACE2, the receptor for the virus. Dr Seheult then goes on to another study from Switzerland. This study looked at 639 critically ill covid10 patients, to determine which factors were most associated with survival or otherwise. So in general they found that this group suffered a ‘moderate’ mortality rate of 24%. To understand the findings will require quite a bit of medico-immunological knowledge, but here goes: they found that ‘PCT and IL-6 levels remained similar in ICU survivors and non-survivors throughout the ICU stay’. PCT is procalcitonin. According to Medscape:

Procalcitonin (PCT) is a biomarker that exhibits greater specificity than other proinflammatory markers (eg, cytokines) in identifying sepsis and can be used in the diagnosis of bacterial infections. Procalcitonin is also produced by the neuroendocrine cells of the lung and intestine and is released as an acute-phase reactant in response to inflammatory stimuli, especially those of bacterial origin. This raised procalcitonin level during inflammation is associated with bacterial endotoxin and inflammatory cytokines.

IL-6 is interleukin-6. An opinion article in Frontiers in Microbiology  entitled ‘The Role of Interleukin-6 During Viral Infections’ describes IL-6:

IL-6 is a pleiotropic cytokine produced in response to tissue damage and infections…  Multiple cell types including fibroblasts, keratinocytes, mesangial cells, vascular endothelial cells, mast cells, macrophages, dendritic cells, and T and B cells are associated with the production of this cytokine….

Pleiotropic cytokines – a cytokine is a type of small protein – affect the activity of multiple cell types. The complex pleiotropic nature of IL-6 unsurprisingly implicates it in both pro-inflammatory and anti-inflammatory effects. So, PCT and Il-6 levels remained similar for these study subjects, but ‘CRP, creatinine, troponin, D-dimer, lactate, neutrophil count, P/F diverged within the first seven days.’  Okay, C-reactive protein (CRP) is produced in the liver, from which it enters the bloodstream, and its levels ‘start to increase very soon after any inflammation or infection affects the body’, according to Australia’s healthdirect website. Creatinine is a waste product found in everyone’s bloodstream, and it’s produced by muscle metabolism. It’s generally filtered out by the kidneys. Too much blood creatinine may be a sign of kidney dysfunction. D-Dimer, the fibrin degradation product, always contains ‘two D fragments of the fibrin product joined by a cross-link’. I won’t try to explain much further at present. Neutrophils, remember, are infection-fighting white blood cells, and P/F ratio, aka PaO2/FiO2 ratio, is, briefly, an assessment of lung function. So with that, and some more, the study looked at levels of different markers most associated with mortality. To quote from the study: 

In contrast to risk factors in hospitalised patients reported in other studies, the main mortality predictors in these critically ill patients were markers of oxygenation deficit, renal and microvascular dysfunction, and coagulatory activation. Elevated risk of bloodstream infections underscores the need to exercise caution with off-label therapies. 

Canto: That last point seems important- it’s all about the blood. Or mostly..?

Jacinta: They presented a number of graphs which Dr Seheult interprets for us, but basically they are all likely to mark higher levels of microthrombi in the patients who died, and this seemed more clearly so in the D-dimer levels. High lactate levels are a sign of anaerobic metabolism, a problem with oxygenation. Ischemic heart disease was also measured, and this has to do with narrowing of the arteries. So blood oxygenation, or lack thereof, and coagulation, which can happen just about anywhere, seems to be happening early, leading to a wide range of symptoms, especially in patients with comorbidities, some of them previously undetected. 

Canto: So we’re moving on to update 96, which starts again with thrombosis due to endothelial damage causing increased production or release of von Willibrand factor (VWF).

Jacinta: Yes, and they’re apparently finding that different blood groups or types – and that’s a topic we could spend a lot of time on – affect the level and activity of VWF. As do other factors, according to Russian researcher Anna Aksenova:

The level and activity of VWF in the blood in people can be different. The lowest values are associated with von Willebrand disease. It is a hereditary blood disease that is characterized by spontaneous bleeding. Additionally, it differs markedly among healthy people. For example, it is higher among: African Americans than among Europeans; in men than in women; in adults than in children; and in the elderly than in middle-aged people. Also, academic papers have described the VWF and blood group relationship—its level is lower among people with blood group 0, and is higher among those with blood group A. The different amount and activity of VWF in people with different blood groups has a very interesting explanation: this protein is modified by oligosaccharide chains of antigenic determinants of the AB0 system (one of the blood group systems), and this affects its stability and activity.

She points out that ‘to date, the way in which the level of VWF is regulated in the blood has not yet been fully studied’, and then she describes some of what we do know, that it’s stored in special organelles (Weibel-Palade bodies) from where it’s secreted in multimeric form. She argues that, in order to determine the level of involvement of VWF in the progress of covid19, ‘large scale and comprehensive research’ needs to be carried out. Another article which is looking at emergency covid19 treatment has the title ‘targeting raised VWF levels and macrophage activation in severe covid19: consider low volume plasma exchange and low dose steroid’. It points out that VWF is such a large protein that it can only really be removed from the body through plasma exchange. This may be a way to reduce thrombosis in serious cases. Another interesting commentary piece is titled ‘microthrombotic complications of covid19 are likely due to embolism of circulating endothelial-derived ultralarge von Willebrand Factor (eULVWF) decorated-platelet strings’. 

Canto: An embolism being a blockage, caused by an embolus. That embolus could be a blood clot (a thrombus) or a fat globule or an air or gas bubble. 

Jacinta: Yes, and VWF can come in these long strings of platelets. In fact the platelets adhere to the strings. Anyway, that’ll do for now. We’ll go on about ivermectin and the Moderna vaccine trials next time. 

References

Coronavirus Pandemic Update 95: Widespread Clotting on Autopsy; New COVID-19 Prognostic Data

Coronavirus Pandemic Update 96: RNA Vaccine; Ivermectin; von Willebrand Factor and COVID-19

https://labtestsonline.org/tests/troponin#:~:text=Troponins%20are%20a%20group%20of,to%20help%20detect%20heart%20injury.

https://www1.racgp.org.au/ajgp/coronavirus/cardiovascular-conditions-and-covid-19#:~:text=Elevated%20biomarkers%3A%20Troponin%20and%20natriuretic,a%20marker%20for%20cardiac%20injury.&text=The%20cause%20of%20troponin%20elevation%20in%20serious%20infection%20is%20multifactorial.

https://www.medscape.com/answers/2096589-179642/what-is-procalcitonin-pct

https://www.frontiersin.org/articles/10.3389/fmicb.2019.01057/full

https://www.medicinenet.com/script/main/art.asp?articlekey=26197

https://www.healthdirect.gov.au/c-reactive-protein-CRP-test

https://medicalxpress.com/news/2020-07-complications-covid-von-willebrand-factor.html

Written by stewart henderson

September 6, 2020 at 1:44 pm

stuff about Covid-19: cytokine problems

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got all that?

Canto: So what are cytokines? They’re ‘signalling proteins, usually less than 80kDa in size’ – that means kilodaltons, and it refers to molecular mass. Proteins have a huge variety of shapes and sizes, the largest being titin, with a mass of 3,816,188.13 Da. I don’t know why they don’t keep to kilodaltons. I presume the daltons measurement is in memory of the pioneering British chemist John Dalton, a truly inspiring character. Cytokines are quite small proteins, I think. Or peptides, which are described on other science sites as not being proteins, or not quite, which is confusing.

Jacinta: We’re looking at a ScienceDirect website which is pretty technical, but it says cytokines regulate many biological functions including those related to innate and acquired immunity. Here’s its ‘operational definition’:

Cytokines can be defined operationally as polypeptides secreted by leukocytes and other cells that act principally on hematopoietic cells, the effects of which include modulation of immune and inflammatory responses.

So peptides are short strings of amino acids, and proteins are longer strings of amino acids, so polypeptides are apparently more than just peptides but not quite proteins. Very weird. Leukocytes are white blood cells, of which there are three main types (I think): monocytes, lymphocytes (T cells and B cells) and granulocytes (neutrophils, eosinophils and basophils). Leukocytes are made in our bone marrow and are found in our blood and lymph. I’d love to learn about lymph one day.

Canto: So leukocytes are part of our immune system, as are the cytokines they secrete. Hematopoietic cells – always worth breaking things down: hema, or haema, always refers to blood, and poiesis, from ancient Greek, essentially means production or bringing into being. Presumably, then, these hematopoietic cells exist in the bone marrow, where they produce leukocytes. And yet… that all seems to mean that cytokines are secreted (and presumably produced) by leukocytes to act on hematopoietic cells that produce leukocytes… It seems a bit circular to me.

Jacinta: Certainly complex. Let’s barge on. The ScienceDirect site has it that cytokines are secreted by many cell types, often at high concentrations, and are mostly involved in cell-to-cell interactions with neighbouring cells. This is called paracrine signalling, as opposed to other forms of signalling (endocrine, juxtacrine and autocrine). However, cytokines can sometimes use those other forms. There are many different groups of cytokines, usually named for their most significant effects, as we see them, but they’re actually pleiotropic, meaning they have each a variety of functions, and those functions can be mediated by other cytokine groups. So, certainly complex, but in terms of their function in response to airways diseases…

Canto: But now I’m hearing that Covid-19 isn’t necessarily an airways disease, or only an airways disease. It may affect the brain and the nervous system, the kidneys, the heart, the blood…

Jacinta: Hmmm, so much more to explore, before we all die. But knowledge is power, the more we know, the more we can defend ourselves. Let’s all be Popperian optimists and rise to the challenge. Here’s an overview, from a 2009 article on cytokines as related to asthma and COPD:

The major classes of cytokines include: pro- and anti-inflammatory cytokines, cytokines of neutrophil and eosinophil recruitment and activation, cytokines derived from T-helper (Th) and T-regulatory (Tregs) cells, and cytokines of T-cell recruitment and growth factors.

The cells mentioned are all leukocytes. But the storm of cytokines may well be causative of those other symptoms found in Covid-19 sufferers, such as blood clots. A very recent article in the Lancet has this to say in reference to what we’re seeing:

the overproduction of early response proinflammatory cytokines (tumour necrosis factor [TNF], IL-6, and IL-1β) results in what has been described as a cytokine storm, leading to an increased risk of vascular hyperpermeability, multiorgan failure, and eventually death when the high cytokine concentrations are unabated over time. Therefore, therapeutic strategies under investigation are targeting the overactive cytokine response with anticytokine therapies or immunomodulators, but this must be balanced with maintaining an adequate inflammatory response for pathogen clearance.

Canto: Wow, I suppose one thing we’ll be learning fast from this pandemic will be a lot more about cytokine production and how it can be abated without risk to the immune system. I wonder if there are any ‘anticytokine therapies’ at present?

Jacinta: Well I’ve read this Lancet article and I can’t pretend to comprehend all that’s in it, but of course it tries to address all we’re concerned about here so I’m going to try to explain it in my way. Hospitalised Covid-19 patients are presenting with pneumonia, ARDS and other respiratory conditions, and sepsis. Sepsis is a broad term, referring to an unbalanced blood immune response which, at its worst, can lead to multiple organ failure. Vascular hyperpermeability, mentioned above, is defined as ‘the excessive leakage of fluid and proteins from blood vessels to the interstitial space‘, being the fluid-filled space around tissue cells. The protease thrombin, which is apparently a coagulant (among other things) and not itself a cytokine, is in normal circumstances tightly regulated in the body by multiple factors, all of which can be impaired by hyperinflammatory conditions. The procoagulant-anticoagulant balance is disrupted, which can lead to microthrombosis and ‘disseminated intravascular coagulation’. Which I think is self-explanatory, and not good. The article refers to ‘raised d-dimer concentrations’ which has to do with fibrin, a fibrous protein involved in blood-clotting. The difficulty is that treatment with ‘endogenous anticoagulants’ has its dangers, shown in previous negative trials. There’s this important factor in respiratory physiology called the ventilation/perfusion (V/Q) ratio, with V being the measure of air getting to the alveoli, and Q the measure of blood getting to the alveoli. A mismatch there can affect the possibility of venous thromboembolism – blood clots, to oversimplify. What this forbiddingly technical Lancet article is suggesting, finally, is that studies conducted on murine [rat/mouse] models of PAR-1 antagonists (PAR-1 being protease-activated receptor, the main thrombin receptor mediating platelet aggregation) have shown some promise, and need to be further investigated tout de suite. Here are the authors’ final words:

Targeting thrombin, coagulation factor Xa or PAR-1, might therefore be an attractive approach to reduce SARS-CoV-2 microthrombosis, lung injury, and associated poor outcomes.

References

https://en.wikipedia.org/wiki/John_Dalton

https://www.sciencedirect.com/topics/neuroscience/cytokines

https://www.medicalnewstoday.com/articles/326701

https://www.cancer.gov/publications/dictionaries/cancer-terms/def/leukocyte

https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30216-2/fulltext

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3049450/

Written by stewart henderson

May 2, 2020 at 4:51 pm

Covid19: world progress, cytokine storms, our plans

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to be explored further

Canto: So while we need to be worried about – and to know something about – the cytokine storm that the Covid19 infection can lead to (and we’ll learn about that soon), there’s also a storm of activity on the SARS-CoV-2-fighting front.

Jacinta: Yes, intravenous zinc was talked about in the Medcram series as an effective tool in fighting viral pneumonia, and a world-first trial is being conducted by Austin Health and Melbourne University to test its effectiveness for Covid-19 sufferers with respiratory problems. We’re still catching up on the Medcram series, and update 52 talks of the drug ivermectin, already on the WHO list of essential medicines. The WHO website, incidentally, is promoting a ‘solidarity’ clinical trial for Covid-19 treatments, involving, singly or in combination, remdesivir, hydroxychloraquine, lopinavir, ritonavir and interferon beta-1a. So that gives some idea of the work that’s going on to fight symptoms and reduce the death rate.

Canto: And, you know, I’ve been feeling guilty about singling out the USA as the worst-case scenario all round. It’s not actually so. It’s not fair to look at total figures and point out that the USA tops the list for Covid19 fatalities, and draw calamitous conclusions. You have to take into account its much larger population compared, for example, to number two on the list, Spain. The US has suffered about 2.5 times the fatalities of Spain, but it has about 7 times the population. In fact, if you look at fatalities as a proportion of population, there are many countries worse off than the USA – namely Spain, Italy, France, the UK, Belgium (the worst hit), the Netherlands, Switzerland, Ireland and Sweden. All European countries, notably.

Jacinta: Yes and I’m sure they’ll all have their particular stories to tell about why this is happening to them, and will be wanting to learn lessons from Taiwan, Hong Kong, South Korea, and even our big faraway island, but I really want to look at solutions, in terms of eradicating the virus, or blocking it, or building up our immunity. Having said that, flattening the curve, and reducing fatalities, is a primary focus, which means continuing the physical distancing and looking for ways to keep economies running while this goes on. In spite of patches of civil libertarian activity here and there, the vast majority of our global population is on the same page with this, I think.

Canto: Well I’m looking at an Axios article from the Johns Hopkins website. It compares global performance under Covid19 to a mock pandemic exercise, Event 201, conducted some six months ago. They’ve found some positives and some negatives in their analysis. Positives – a greater degree of compliance with physical distancing measures than expected, ‘the degree of surge capacity augmentation in the health care system which has been possible’, and the rapid growth of international collaboration among scientists, leading to a quickened progress of trials for possible treatments. Negative – disparate and often contradictory messages from authorities – mostly political authorities – leading to confusion and distrust of governments and other institutions. This is partially explained by the complexity of the virus itself, which has made it difficult to characterise to the general public, and to be fully understood by non-medical authorities, such as political leaders.

Jacinta: It’s a weird situation, as there’s no end in sight, everyone’s worried about ending restrictions too soon, yet everyone’s worried about the economy, and those countries, like Australia, that are heading towards winter, are bracing for heightened problems, while northern hemisphere countries are hoping for summer’s relief but worried about the autumn when it might be hard to cope with a second outbreak, should it come. And medicos are warning that expectations of a vaccine in eighteen months might be overly optimistic. But I want to be optimistic – I want to look at anything that’ll reduce symptoms and save lives. One treatment, among many others it should be noted, is hydroxychloraquine, which is being given so much of a bad press, because of its being over-hyped by a Trump administration intent on getting political points for a silver-bullet cure. There have already been a number of small, less-than-gold-standard studies, some in which the drug is combined with the antibiotic azithromycin, and the results appear to be all over the place. We’re still awaiting the results of randomised, placebo-controlled, double-blinded studies, which are under way.

Canto: I note that a couple of reports on chloraquine and hydroxychloraquine on the JAMA website have been taken down, I suspect because of all the politicising. That’s a shame. Anyway I mentioned the cytokine storm at the beginning of this post, so I’ll try to comprehend it. A clue to the meaning comes in this mid-March article on the Lancet website. In an early sentence it mentions ‘cytokine storm syndrome’, and in the following sentence refers to the treatment of ‘hyperinflammation’. It seems the two terms are interchangeable. Another term, in the very next sentence, is ‘a fulminant and fatal hypercytokinaemia’….

Jacinta: Sounds like they’re just showing off.

Canto: Please don’t say that about our frontline covidtroops. Okay, a better site for understanding cytokines and their storms is this from New Scientist. As we’ve guessed, it’s an over-reaction of the immune system, sometimes fatal. Cytokines are small proteins, produced throughout the body, which trigger inflammation as an immune response. Sometimes the intensity of the cytokine response results in hyperinflammation. So you might say the cytokine storm is the cause and hyperinflammation the effect.

Jacinta: So this raises questions. For example, why do some have what seems an over-production of these cytokines and others don’t, in response to SARS-CoV-2 in particular? And what do these cytokines actually do to cause inflammation?

Canto: You’re asking me? Well, it’s conjectured that younger people don’t have the developed immune system that produces all these cytokines, and that’s why you don’t see symptoms. But that raises the question – do others have over-developed immune systems, but maybe only for this particular virus? Is there a general goldilocks level?

Jacinta: And is there a way of distinguishing between those who succumb to the hyperinflammation, which in turn can cause acute respiratory distress syndrome (ARDS), and those who succumb to the virus itself? Or is it always the immune response that does people in?

Canto: I don’t think so. If the immune response doesn’t work at all, I suspect the virus will spread like a cancer to the rest of the body?

Jacinta: That can’t be right. That’d mean those kids who don’t suffer the cytokine storm, or any immune reaction, would remain infected until it spread through their bodies and they dropped dead. That definitely isn’t happening.

Canto: No, you’re right – they’re developing antibodies, presumably, (and that’s a whole other story), without going through much in the way of suffering. In fact, children’s apparent immunity to the virus is something of a mystery that demands further research. If everyone could develop that kind of immunity…

Jacinta: So many questions we can’t answer. I mean, not just the myriad questions we, as dilettantes and autodidacts, can’t answer, but the fewer but many questions epidemiologists, virologists and ICU workers can’t answer. But I propose that we continue to try and educate ourselves and explore, in our feeble but earnest way. I propose that we dedicate this blog, for the foreseeable, to exploring terms and conditions, so to speak, and treatments, such as ‘cytokine’, ‘ACE-2’, ‘hypoxia’ and ‘quercetin’ and how they relate to or are affected by the Covid-19 infection. Like putting pieces together in a jigsaw puzzle, sort of. It might help us being overwhelmed by the whole picture.

Canto: Okay, let’s try it.

References

Coronavirus pandemic update 52, Medcram youtube video

https://coronavirus.jhu.edu/news

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30628-0/fulltext

https://www.newscientist.com/term/cytokine-storm/

https://www.centerforhealthsecurity.org/event201/

https://www.axios.com/coronavirus-global-pandemic-preparation-fdce4bff-f1d3-433d-bceb-cc20ac869102.html

https://jamanetwork.com/journals/jama/pages/coronavirus-alert

Written by stewart henderson

April 29, 2020 at 11:55 am